A glacial valley cross-sectional shape is a U shape whereas a stream valley is usually a V shape. The U shape comes from the scouring action of the alpine glaciers which carries rocks with it which can abrade the walls of the valley and the glacier occupies the whole valley so scours out such a shape whereas the stream cuts down and water washes in from the sides of the valley into the stream or river creating the V shape.
Due to a decrease in the supply of food and other resources for fish population their population will start to decline, some will migrates in the search for food while there may compete for the remaining resources. Impacting their population density and his may lead to the death of fishes, some of which may be eaten by other bigger fish.
